1. Field of the Invention
The present invention relates to a position detecting system, a speaker system, and a user terminal apparatus, and more particularly to a position detecting system which detects the position of a user as a listener in a speaker system comprised of a plurality of speakers.
2. Description of the Related Art
Conventionally, in a speaker system comprised of a plurality of speakers, the position of a user as a listener is detected, and a sound image is formed according to the detected position so that the optimum sound field can be obtained for the user. Particularly in an array speaker system, delays to be added to sound signals for input to respective speakers are controlled so as to give directivity to sounds to be output, and sound beams formed as a result are reflected on walls to form a three-dimensional sound field. Accordingly, detecting the position of a user has become increasingly important in setting suitable beam parameters which are parameters for controlling sound beams.
As an example of conventional position detecting techniques, a stereo sound restoring system disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H05-091597 is constructed such that a listener carries a sound transmitting device, receiving circuits are provided close to respective ones of right and left speakers, and the listener's position is detected based upon the reception level of sound transmitted from the sound transmitting device when it is received by the receiving circuits. As another example of conventional position detecting techniques, detecting the position of a person using a plurality of special-purpose human body sensors is disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H05-137200. As still another example of conventional position detecting techniques, identifying the position of a viewer by performing processing on an image picked up by a video camera is disclosed in U.S. Pat. No. 6,741,273.
The above conventional position detecting techniques, however, require installing special-purpose receiving circuits, sensor, camera, and so forth at suitable positions and also have problems described below.
According to the position detecting technique disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H05-091597, the sound transmitting device to be carried by a listener is required to be equipped with a speaker for outputting sound and a power amplifier for driving the speaker. Also, the speaker is required to be equipped with a sound receiving circuit in addition to its essential speaker capability. As a result, the sound transmitting device is large-sized. According to the position detecting technique disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H05-137200, when, for example, the positions of a plurality of persons are detected, complicated processing has to be performed to detect the positions of the persons since the plurality of human body sensors (infrared sensors) are used. According to the position detecting technique disclosed in U.S. Pat. No. 6,741,273, devices such as a video camera and an image processing device are needed, resulting in an increase in the costs of both hardware and software.